Maleic acid anhydride reactant

Maleic anhydride (2,5-furandione) is obtained as a by-product in the production of phthalic anhydride and by the vapor phase oxidation of butylene or crotonaldehyde. It is also obtained by the dehydration of maleic acid and by the oxidation of benzene. Maleic anhydride is used for the production of unsaturated polyester resin. This reactant, like most reactants, is fairly toxic and should be treated as such. 

Uses. About 35% of the isophthahc acid is used to prepare unsaturated polyester resins. These are condensation products of isophthahc acid, an unsaturated dibasic acid, most likely maleic anhydride, and a glycol such as propylene glycol. The polymer is dissolved in an inhibited vinyl monomer, usually styrene with a quinone inhibitor. When this viscous hquid is treated with a catalyst, heat or free-radical initiation causes cross-linking and sohdification. A range of properties is possible depending on the reactants used and their ratios (97). 

Polyestetification involving insoluble reactants such as isophthaUc acid is normally carried out in two-stage reactions, in which isophthaUc acid reacts first with the glycol to form a cleat melt. The balance of the reactants, including maleic anhydride, is then added to complete the polyester polymer, thus avoiding longer cycle times and some discoloration. 

Contact time between the reactants and the catalyst is about a tenth of a second. The reaction gases—mainly phthalic anhydride, carbon dioxide, and water—are cooled, condensed, and purified in stainless steel facilities. Phthalic anhydride solidifies at 269°Fj so the purified (99.5%) product can be stored in its molten form or cooled and flaked. Minor amounts of by-products, maleic anhydride, phthalic acid, and benzoic acid are also produced. 

Figure 2 Selectivity at 30% conversion for the reactions indicated as a function ofD°H C-H(reactant) - D°HC-h or c-c (product). 1 ethylbenzene to styrene 2. 1-butene to 1, 3-butadiene 3. toluene to benzoic acid 4. acrolein to acrylic acid 5. ethane to enthylene 6. n-butane to maleic anhydride 7. benzene to phenol 8. toluene to benzaldehyde 9. propene to acrolein 10. 1-butene to 2-butanone 11. isobutene to isobutene 12. methanol to formaldehyde 13. methacrolein to methacyclin acid 14. propane to propene 15. ethanol to acetaldehyde 16. isobutene to methacrolein 17. n-butane to butene 18. benzene to maleic anhydride 19. propane to acrolein 20. methane to ethane 21. ethane to acetaldehyde, 22. isobutane to methacrylic acid 23. methane to formaldehyde 24. isobutane to methacrolein.

M-Acetylsaccharinyl acid derivatives 408, which are structurally related to COX-2 inhibitor celecoxib, were designed and synthesised [133] from M-saccharinyl acetate 407a, prepared via the reaction of ethyl bromoacetate with sodium saccharin by heating the reactants in DMF (see [133]). Its transformation into the corresponding hydrazide 407b and subsequent reaction with ethyl acetoacetate, /3-diketones and maleic anhydride, afforded the heterocyclic compounds 408 [134] (Scheme 97). 

The selectivity to the product of partial oxidation is a function of the structure of the reactant. From n-butane and n-pentane the seleetivity to maleic anhydride and to maleic plus phthalic anhydrides, respectively, is high, while from ethane the prevailing products are either ethylene or earbon oxides (depending on the reaetion conditions) acetic acid is formed in rather low amounts. From propane very low amounts of acrylic acid are formed, and carbon oxides prevail. These differences can be attributed to the formation of very stable products... 

Figure 3 Selectivity in product versus D H c-H reactant D°H c-H or C-C product at 30% conversion. 1, Ethylbenzene to Styrene. 2, 1-Butene to Butadiene. 3, Acrolein to Acrylic Acid. 4, Ethane to Ethylene. 5, n-Butane to Maleic Anhydride. 6, Propene to Acrolein. 7, Methanol to Formaldehyde. 8, Ethanol to Acetaldehyde. 9, Propane to Propene. 10, n-Butane to Butenes. 11, Propane to Acrolein. 12, Methane to Ethane. 13, Ethane to Acetaldehyde. 14, Methane to Formaldehyde [1].

Later, Lewis acids were suggested as catalysts for Diels-Alder addi-tions in the case of the reaction of anthracene with maleic anhydride the acceleration due to AICI3 was estimated to be of the order of 10 . As has been mentioned (Section 4.1.1), in the presence of Lewis acids endo adducts are more favoured than in uncatalysed reactions, and there is more selectivity in orientation when unsymmetrical dienes and dienophiles add to each other furthermore, with an optically active reactant, asymmetric induction can be stronger in the catalysed reaction (Table 4, footnote b). it should be appreciated that substrates sensitive to AICI3 and similar catalysts are always polar molecules, usually containing carboxyl or carbonyl groups, to which Lewis acids can become bound. 

Heterogeneous catalytic oxidation is a well studied and industrially useful process. Industrial catalytic oxidation of vapors and gases is a very broad field and is dealt with in several texts and review articles. Catalytic oxidation, both partial and complete, is an important process for such reactions as the partial oxidation of ethene and propene, ammoxidation of propene to acrylonitrile, maleic anhydride production, production of sulfuric acid, and oxidation of hydrocarbons in automotive exhaust catalysts. By far, the majority of oxidation catalysts and catalytic oxidation processes have been developed for these industrially important partially oxidized products. However, there are important differences between the commercial processes and the complete catalytic oxidation of VOCs at trace concentrations in air. For instance, in partial oxidation, complete oxidation to CO2 and H2O is an undesirable reaction occurring in parallel or in series to the one of interest. Other differences include the reactant concentration and temperature, the type of catalyst used, and the chemical nature of the oxidizable compound. Approximate ranges of the major independent variables of interest in this review are shown in Table 1. 

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